Segmented Charge-Storage Blocks in 3D NAND for Data Retention
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Solution Overview
Problem
Conventional NAND memory architectures face data retention issues due to charge migration between memory cells caused by charge-trapping material extending across multiple cells, leading to inefficient charge storage and retrieval.
Innovation Solution
Incorporating breaks in the charge-trapping material between memory cells and using a vertical stack of alternating insulative and conductive levels with tailored channel and charge-storage materials to impede charge migration, allowing for controlled charge storage and retrieval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If charge-trapping material is used to store charge in NAND memory cells, then charge storage capacity is improved, but charge migration between adjacent memory cells occurs causing data retention issues
Solution Approach 1:
The charge-trapping material is segmented into discrete portions, with each portion located within a specific memory cell and separated from adjacent cells by spacer material. This segmentation prevents charge migration between cells while maintaining storage capacity within each isolated segment.
Solution Approach 2:
The harmful charge-trapping material is extracted from continuous form and replaced with discrete, isolated portions surrounded by spacer material. This extraction of the material from its continuous state eliminates the migration pathway while preserving the charge storage function in each isolated segment.
2Quantity of substance
If vertically-stacked memory cells are implemented to increase density, then packing density is improved, but charge migration between cells in the stack increases
Solution Approach 1:
Spacer material is introduced as an intermediary substance between vertically-stacked memory cells. This intermediary layer physically separates the charge-trapping material portions in adjacent cells, blocking charge migration pathways while allowing the vertical stacking architecture to maintain high packing density.
3Ease of manufacture
If continuous charge-trapping material is used across multiple memory cells, then manufacturing simplicity is maintained, but charge storage efficiency decreases due to migration
Solution Approach 1:
The charge-trapping material is segmented into discrete portions rather than used continuously. Each segment is isolated within a specific memory cell by spacer material, preventing charge migration and improving storage efficiency. The segmentation is achieved through standard deposition and etching processes that form the spacer material between cells.
Data Source
AI summary
Some embodiments include a NAND memory array having a vertical stack of alternating insulative levels and conductive levels. The conductive levels include terminal regions, and include nonterminal regions proximate the terminal regions. The terminal regions are vertically thicker than the nonterminal regions, and are configured as segments which are vertically stacked one atop another and which are vertically spaced from one another. Blocks are adjacent to the segments and have approximately a same vertical thickness as the segments. The blocks include high-k dielectric material, charge-blocking material and charge-storage material. Channel material extends vertically along the stack and is adjacent to the blocks. Some embodiments include integrated assemblies. Some embodiments include methods of forming integrated assemblies.